This invention relates to injection molding elongated bodies and especially continuous lengths of flat or circumferentially and longitudinally curved precured tire treads. These lengths of tread can be made by increments and coiled into rolls for storage and shipping to the place of use. The tread is cut to the desired length at the time of use for adherence to a new tire casing or to a tire to be retreaded by a suitable adhesive.
Heretofore, it has been proposed to make a continuous tread by feeding a strip of unvulcanized rubber onto a rotating cylinder and then enclosing the strip with mold segments rotating with the cylinder and radially movable into engagement with the cylinder. The tread is cured by compression molding and then removed from the cylinder as the mold segments are moved radially away from the cylinder. This process is not adaptable for injection molding where the tread must be formed and cured by increments and therefore there must be provision made to adhere the previously cured section to the section being injected and cured.
Continuous tire treads have also been made by passing an extruded rubber strip between cooperating mold segments carried by respective endless belts which apply suitable temperatures and pressure to the strip to produce the surface designs. The molded, uncured rubber strip is then removed from the molds and cured by applying radiation or heat. Here again, the process is not adaptable for injection molding.